JP2007238767A - Lubricant composition, retractable shaft, and steering device using the shaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lubricant composition preventing occurrence of slip stick and keeping always good lubrication performance when used for lubrication of a retractable shaft and loaded with high bearing pressure, to provide a retractable shaft having a pair of shaft elements lubricated therebetween with the lubricant composition, and to provide a steering device using the retractable shaft as an intermediate shaft. <P>SOLUTION: The lubricant composition comprises a base oil having 1,500-13,000 mm<SP>2</SP>/s (40°C) kinematic viscosity and polytetrafluoroethylene as a thickener. The retractable shaft 5 is lubricated between a pair of shaft elements 51 and 52 with the lubricant composition. The steering device 1 is inserted the retractable shaft between a steering shaft 3 and a rack and pinion mechanism A as the intermediate shaft. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  INDUSTRIAL APPLICABILITY The present invention is suitable for lubricating between the two shaft members of a telescopic shaft that includes a pair of shaft members that are extendable in the axial direction and coupled so as to be integrally rotatable in a rotation direction around the shaft. The present invention relates to a lubricant composition, the telescopic shaft, and a steering device incorporating the telescopic shaft.

  As a power steering apparatus (EPS) for automobiles, there is a column type EPS that uses the rotational force of an electric motor provided in a column. In column-type EPS, the shaft can be expanded and contracted in the axial direction as an intermediate shaft for connecting a steering shaft connected to a steering wheel as a steering member and a steering mechanism such as a rack and pinion mechanism. In addition, a telescopic shaft including a pair of shaft members that are coupled so as to be integrally rotatable in a rotation direction around the shaft has become widespread.

In column type EPS, using the telescopic function of the telescopic shaft, the assembly workability can be improved by arbitrarily changing the distance between the steering shaft and the steering mechanism when assembling to the automobile. When the automobile travels, the relative displacement between the steering shaft and the steering mechanism is absorbed.
In general, a spline or a serration is employed as the coupling structure of the telescopic shaft. For example, of the pair of shaft members, a male spline (external spline) portion is provided at an end portion of one shaft member (inner shaft member), and the male spline is disposed at an end portion of the other shaft member (outer shaft member). A cylindrical female spline (internal spline) part is formed, the male spline part is inserted into the female spline part, and both shaft members can be expanded and contracted in the axial direction and centered on the axis A telescopic shaft is configured by being coupled to be rotatable in the rotation direction.

In this case, if there is no clearance between both the spline parts, the male spline part cannot be inserted into the female spline part to assemble the telescopic shaft. However, when the clearance is provided, the two shaft members are displaced relative to each other in the radial direction and the circumferential direction, thereby generating a rattle sound, which causes discomfort to the driver (see Patent Document 1).
JP 2001-50293 A (columns 0002 to 0005)

  Therefore, a resin coating is applied to at least one surface of both the spline portions to reduce the clearance and lubricate with a lubricant composition such as grease. However, recently, as the use of column-type EPS for large displacement vehicles has expanded, the load (torsional rigidity) applied to the steering column during steering tends to increase. If normal grease is used for lubrication, stick slip due to oil film breakage will occur, especially when returning the steering wheel. This creates a new problem of discomfort.

  An object of the present invention is to use a lubricant composition for lubrication of a telescopic shaft to prevent the occurrence of a slip stick when a high surface pressure is applied, and to always maintain good lubrication performance. Another object of the present invention is to provide a telescopic shaft that is lubricated between the pair of shaft members using the lubricant composition, and a steering device that uses the telescopic shaft as an intermediate shaft.

The present invention relates to a lubricant composition for lubricating a space between both shaft members of a telescopic shaft including a pair of shaft members that are extendable in the axial direction and coupled so as to be integrally rotatable in a rotation direction around the shaft. A base oil having a kinematic viscosity of 1500 to 13000 mm ² / s (40 ° C.) and polytetrafluoroethylene as a thickener. The content ratio of polytetrafluoroethylene is preferably 20 to 50% by weight.

The telescopic shaft of the present invention includes a pair of shaft members that are extendable in the axial direction and coupled so as to be integrally rotatable in a rotation direction centered on the shaft, and between the two shaft members is the above-described present invention. It is characterized by being lubricated with the lubricant composition.
The present invention further includes a steering member, a steering shaft connected to the steering member, an intermediate shaft connected to the steering shaft via a universal joint, and a pinion shaft connected to the intermediate shaft via a universal joint. A steering device having a rack and pinion mechanism for converting the rotation of the pinion shaft into a linear motion of the rack bar to steer the steered wheel, and incorporating the telescopic shaft of the present invention as an intermediate shaft It is characterized by.

According to the present invention, since the kinematic viscosity of the base oil at 40 ° C. is limited to 1500 mm ² / s or more, polytetrafluoroethylene (PTFE) that also functions as a solid lubricant is used as a thickener. The lubricant composition can be used, for example, to lubricate a telescopic shaft, and when high surface pressure is applied, the oil film is cut and stick slip can be prevented from occurring. In addition, since the kinematic viscosity of the base oil is limited to 13000 mm ² / s or less, for example, a telescopic shaft is incorporated into a column type EPS and expanded and contracted to change the distance between the steering shaft and the steering mechanism. However, it is possible to prevent the slide load from becoming too high when assembling the vehicle, and to improve the workability.

(Lubricant composition)
The lubricant composition of the present invention comprises a base oil having a kinematic viscosity of 1500 to 13000 mm ² / s (40 ° C.) and PTFE as a thickener. In the present invention, the kinematic viscosity of the base oil at 40 ° C. is limited to 1500 to 13000 mm ² / s for the following reason.

That is, when the kinematic viscosity of the base oil at 40 ° C. is less than 1500 mm ² / s, the viscosity of the lubricant composition becomes too low. For example, even if PTFE is contained as a thickener, for example, the lubricant composition When an object is used for lubrication of a telescopic shaft and a high surface pressure is applied, it becomes impossible to prevent the occurrence of stick slip due to oil film breakage. On the other hand, when the kinematic viscosity of the base oil at 40 ° C. exceeds 13000 mm ² / s, the viscosity of the lubricant composition becomes too high. As a result, the slide load becomes too high when assembling the vehicle while changing the distance between the steering shaft and the steering mechanism, and the workability thereof is lowered. In the worst case, there is a problem that the above assembling work cannot be performed manually.

On the other hand, if the kinematic viscosity of the base oil is 1500 to 13000 mm ² / s, the synergistic effect with the use of PTFE that also functions as a solid lubricant as described above is due to oil film breakage. In addition to preventing the occurrence of stick-slip, for example, work when assembling in a car while incorporating a telescopic shaft as an intermediate shaft into a column-type EPS and expanding and contracting to change the distance between the steering shaft and the steering mechanism Can be improved. In addition, in consideration of further reliably preventing the occurrence of stick-slip due to oil film breakage and further improving the workability of assembling the column type EPS, the kinematic viscosity of the base oil is particularly within the above range. 2000 to 7500 mm ² / s.

  As the base oil, among various conventionally known base oils such as synthetic hydrocarbon oils, silicone oils, fluorine oils, ester oils, ether oils and mineral oils, various kinematic viscosities fall within the above range. Although a base oil can be used, in particular, when a resin coating is applied to at least one surface of the male spline part and the female spline part, a synthetic hydrocarbon oil having a low aggressiveness against the resin coating is preferable, Polyalphaolefin oil is preferably used.

  As the thickener, PTFE is used as described above. For example, when a thickener other than PTFE, such as a metal soap thickener, is used, the effect of preventing stick slip due to oil film breakage can be obtained even if the viscosity of the base oil is within the above range. Absent. This is because a thickener other than PTFE does not have a function as a solid lubricant. However, in the total amount of the thickener, in order to obtain a lubricant composition having a predetermined viscosity characteristic (consistency, etc.) in a range that does not impair the above-mentioned effect due to the blending of the PTFE as a thickener. It is also possible to use other thickeners together with PTFE in such a range that the content ratio of PTFE is too small and the effect of preventing the occurrence of stick-slip due to oil film breakage cannot be obtained.

  As PTFE, any of various grades of PTFE that can be used as a thickener in which very fine spherical PTFE fine particles are dispersed in an arbitrary organic solvent can be used. As described above, the content of PTFE as a thickener is preferably 20 to 50% by weight, more preferably 45 to 50% by weight, based on the total amount of the lubricant composition. If the PTFE content is less than this range, there is a possibility that the effect of preventing the occurrence of stick slip due to oil film breakage due to blending of the PTFE may not be sufficiently obtained. Conversely, when the content exceeds 50% by weight. For example, when a telescopic shaft is incorporated into a column type EPS as an intermediate shaft and expanded and contracted to change the distance between the steering shaft and the steering mechanism, the slide load becomes too high. The workability may be reduced.

  The lubricant composition of the present invention further includes solid lubricants such as molybdenum disulfide and graphite, extreme pressure additives such as phosphorus-based and sulfur-based, antioxidants such as tributylphenol and methylphenol, if necessary. A rust inhibitor, a metal deactivator, a viscosity index improver, an oily agent, and the like may be added. The consistency of the lubricant composition is represented by NLGI (National Lubricating Grease Institute) number. 2-No. 00, especially no. 2-No. 1 is preferred.

(Extensible shaft)
The telescopic shaft of the present invention includes a pair of shaft members that are extendable in the axial direction and coupled so as to be integrally rotatable in a rotation direction around the shaft, and between the two shaft members, the lubrication of the present invention is provided. It is characterized by being lubricated with an agent composition. As the telescopic shaft itself, those having various conventionally known structures can be employed.

FIG. 1 is a perspective view showing a male spline portion 51a provided at an end of an inner shaft member 51 constituting an extendable shaft 5 of an example of an embodiment of the present invention. FIG. 2 is a perspective view of the outer shaft member 52 that constitutes the telescopic shaft 5 together with the outer shaft member 51, with a part of a cylindrical female spline portion 52a provided at the end cut away.
Referring to FIG. 1, a large number of keys 51 b are arranged on the outer peripheral surface of the end portion of the inner shaft member 51 connected to the outer shaft member 52 from the outer peripheral surface outward in the radial direction. A male spline portion 51a is formed so as to protrude in parallel with the axial direction of 51 and at equal intervals in the circumferential direction. Referring to FIG. 2, the outer shaft member 52 has an end 52c connected to the inner shaft member 51 formed in a cylindrical shape into which the male spline portion 51 is inserted, and an inner peripheral surface of the tube. A large number of key grooves 52b meshed with the key 51b of the male spline portion 51 from the inner peripheral surface outward in the radial direction are parallel to the axial direction of the outer shaft member 52 and in the circumferential direction. A female spline portion 52a is formed by being recessed at equal intervals.

Then, by inserting the male spline portion 51a into the female spline portion 52a while engaging the key 51b constituting the male spline portion 51a with the key groove 52b constituting the female spline portion 52a, both shaft members 51, 52 are inserted. However, it can be expanded and contracted in the axial direction, and is connected so as to be able to transmit power in the rotational direction around the axis.
A clearance is set in the meshing portion between the key 51b of the male spline portion 51a and the key groove 52b of the female spline portion 52a as in the prior art. Further, in order to reduce the clearance, it is preferable that at least one surface of the male spline portion 51a and the female spline 52a is coated with a resin as in the conventional case. Examples of the resin that forms the resin coating include oil-resistant thermoplastic resins such as nylon resins, olefin resins, fluorine resins, and polyester resins, epoxy resins, phenol resins, and thermosetting polyester resins. And thermosetting resins such as thermosetting acrylic resins.

Among these, examples of the nylon resin include PA6, PA66, PA46, PA11, PA12, and the like, and aromatic polyamides represented by PPA (polyphthalamide) can also be used. Examples of the olefin resin include PE (polyethylene) such as HDPE (high density polyethylene) and UHDPE (ultra high density polyethylene), and PP (polypropylene). Fluorocarbon resins include PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer), FEP (tetrafluoroethylene / hexafluoropropylene copolymer), ETFE (tetrafluoroethylene / ethylene). Copolymer) and the like. Examples of polyester resins include PET (polyethylene terephthalate), PBT (polybutylene terephthalate), and the like. To these resins, solid lubricants such as PE (polyethylene), PTFE (polytetrafluoroethylene), and MoS ₂ (molybdenum disulfide), and fillers such as calcium carbonate and talc may be added.

Then, the engaging portion of the key 51b of the male spline portion 51a and the key groove 52b of the female spline portion 52a is filled with the lubricant composition of the present invention, and the engaging portion is lubricated, so that it can expand and contract. A shaft 5 is configured.
Such a telescopic shaft 5 is incorporated into a column type EPS as an intermediate shaft and expanded and contracted, for example, by the function of the lubricant composition of the present invention filled in the meshing portion, and the distance between the steering shaft and the steering mechanism Since the slide load does not become too high when assembling to the automobile while changing the above, the workability of the above work can be improved. Further, after the assembly, when the column type EPS is steered, even if a high surface pressure is applied to the engagement portion between the key 51b of the male spline portion 51a and the key groove 52b of the female spline portion 52a, stick slip due to oil film breakage does not occur. Therefore, it is possible to prevent the driver from feeling uncomfortable by generating a slip noise particularly when the steering wheel is returned. The configuration of the telescopic shaft of the present invention can be suitably applied to the intermediate shaft of the column type EPS as described above, and can also be applied to a steering shaft of the same column type EPS.

(Steering device)
FIG. 3 is a schematic configuration diagram of a column type EPS 1 as an example of the embodiment of the steering device of the present invention. Referring to FIG. 3, a column type EPS 1 includes a steering shaft 3 to which a steering wheel 2 as a steering member is connected, an intermediate shaft 5 connected to the steering shaft 3 via a universal joint 4, and an intermediate shaft. As a steered shaft that extends in the left-right direction of the automobile, has a pinion shaft 7 connected to 5 through a universal joint 6 and rack teeth 8a that mesh with pinion teeth 7a provided in the vicinity of the end of the pinion shaft 7. And a rack bar 8. The pinion shaft 7 and the rack bar 8 constitute a rack and pinion mechanism A as a steering mechanism.

  The rack bar 8 is supported in a linearly reciprocable manner in a housing 9 fixed to the vehicle body via a plurality of bearings (not shown). Further, both end portions of the rack bar 8 protrude to both sides of the housing 9, and tie rods 10 are coupled to the respective end portions. Each tie rod 10 is connected to a corresponding steering wheel 11 via a corresponding knuckle arm (not shown). When the steering wheel 2 is operated and the steering shaft 3 is rotated, this rotation is converted into a linear motion of the rack bar 8 along the left-right direction of the automobile by the pinion teeth 7a and the rack teeth 8a. 11 is steered.

  The steering shaft 3 is divided into an input-side upper shaft 3 a that is continuous with the steering wheel 2 and an output-side lower shaft 3 b that is continuous with the pinion shaft 7, and both shafts 3 a and 3 b are the same via a torsion bar 12. Are connected to each other so as to be rotatable relative to each other. Further, the torsion bar 12 is provided with a torque sensor 13 for detecting a steering torque from a relative rotational displacement amount between the shafts 3a and 3b. The torque detection result of the torque sensor 13 is an ECU (Electric Control). Unit: Electronic control unit) 14.

  The ECU 14 drives and controls the steering assist electric motor 16 via the drive circuit 15 based on a torque detection result, a vehicle speed detection result given from a vehicle speed sensor (not shown), and the like. The output rotation of the electric motor 16 is decelerated via the speed reducer 17 and transmitted to the pinion shaft 7 and converted into a linear motion of the rack bar 8 to assist steering. The speed reducer 17 is a worm shaft (small gear) 18 as an input shaft that is rotationally driven by the electric motor 16, and a worm wheel that meshes with the worm shaft 18 and is connected to the lower shaft 3 b of the steering shaft 3 so as to be integrally rotatable. (Large gear) 19.

  By incorporating the telescopic shaft of the present invention as the intermediate shaft 5 among the above parts, a column type EPS 1 as a steering device of the present invention is configured. Such a column-type EPS is used when the intermediate shaft 5 is expanded and contracted by the function of the telescopic shaft as the intermediate shaft 5, and the distance between the steering shaft 3 and the steering mechanism is changed and assembled to the automobile. Since the slide load does not become too high, the workability of the above work can be improved. Further, after the assembly, when the column type EPS is steered, even if a high surface pressure is applied to the engaging portion between the key 51b of the male spline portion 51a and the key groove 52b of the female spline portion 52a, stick slip due to oil film breakage does not occur. Therefore, in particular, it is possible to prevent the driver from feeling uncomfortable by generating a slip sound when the steering wheel 2 is returned.

  In addition, the structure of this invention is not limited to the thing of the example demonstrated above. For example, the telescopic shaft is not limited to the engagement of the male spline portion 51a and the female spline portion 52a shown in FIGS. 1 and 2, and for example, the outer peripheral surface of the inner shaft member and the outer shaft member A rolling groove along the axial direction is formed on the inner peripheral surface, and a plurality of balls can be freely rolled in the groove, and both shaft members can be expanded and contracted in the axial direction via the balls. In addition, a so-called ball spline structure that is coupled so as to be integrally rotatable in the rotation direction about the shaft may be employed.

  Also in this case, the above-mentioned rolling groove is filled with the lubricant composition of the present invention and lubricated between the rolling groove and the ball, thereby causing stick-slip between the two due to oil film breakage. In addition to preventing the occurrence, for example, the telescopic shaft is incorporated into the column-type EPS as an intermediate shaft, and is expanded and contracted to improve the workability when assembling to an automobile while changing the distance between the steering shaft and the steering mechanism can do.

  Further, the steering device in which the telescopic shaft of the present invention is incorporated as an intermediate shaft is not limited to the column type EPS 1 shown in FIG. 3, and other types of EPS and a normal steering device having no steering assist function. There may be. In addition, various design changes can be made without departing from the scope of the present invention.

Examples 1-5:
As a base oil, kinematic viscosity at 40 ° C. is 1500 mm ² / s (Example 1), 2054mm ² / s (Example ^2), 5548mm 2 / s (Example 3), 7414mm ² / s (Example 4), Alternatively, poly α-olein oil of 12500 mm ² / s (Example 5) is used, and PTFE is used as a thickening agent. These two components are blended so that the PTFE content is 45% by weight. Thus, the lubricant compositions of Examples 1 to 5 were prepared.

Comparative Examples 1 and 2:
A poly α-olein oil having a kinematic viscosity at 40 ° C. of 1000 mm ² / s (Comparative Example 1) or 13340 mm ² / s (Comparative Example 2) is used as a base oil, and PTFE is used as a thickener. These components were blended so that the PTFE content was 45% by weight, and the lubricant compositions of Examples 1 to 5 were prepared.

Comparative Example 3:
Poly α-olein oil having a kinematic viscosity at 40 ° C. of 3500 mm ² / s is used as the base oil, and silica is used as the thickener. Both components are mixed so that the silica content is 30% by weight. The lubricant composition of Comparative Example 3 was prepared.
Comparative Example 4:
A poly α-olein oil having a kinematic viscosity at 40 ° C. of 5000 mm ² / s is used as the base oil, and a Li soap thickener is used as the thickener. A lubricant composition of Comparative Example 4 was prepared by blending so that the content ratio of the agent was 10% by weight.

Characteristic Test FIG. 4 is a diagram showing an outline of a test apparatus used for evaluating the characteristics of the lubricant compositions prepared in the above Examples and Comparative Examples. Referring to FIG. 4, the test apparatus includes an inner shaft member 51 and an outer shaft member 52 constituting the telescopic shaft 5 in the meshing portion of the male spline portion 51a and the female spline portion 52a. In the state filled with the lubricant composition prepared in the example, the ends 51c of the inner shaft member 51 opposite to the side on which the male spline part 51a is provided are connected to each other via the torque meter 20. A torque load member that is connected to a drive shaft 21 that can reciprocate in the axial direction indicated by a solid arrow in the figure and that can rotate the outer shaft member 52 in a rotational direction about the central axis of the drive shaft 21 (see FIG. (Not shown).

The torque load member of the test apparatus is rotated in one direction around the central axis of the drive shaft 21, so that the male spline portion 51a and the female spline portion 52a of the inner shaft member 51 and the outer shaft member 52 are engaged with each other. When a sliding load applied to the inner shaft member 51 is measured using a torque meter when the drive shaft 21 is reciprocated in the axial direction while maintaining a state in which a constant torsion torque is applied to the portion, FIG. The graph which shows the relationship between the stroke amount of the axial direction of the inner shaft member 51 shown in 3 and a slide load can be obtained. From this graph, the following characteristics were evaluated by observing the slide load magnitude L ₁ at the start, the magnitude L ₂ at the time of sliding, and the waveform at the time of sliding. The evaluation was performed both when the drive shaft 21 moved forward (above the horizontal axis in the figure) and during backward movement (below the horizontal axis).

Slide load (at start-up): A load with a slide load L ₁ at start-up of 325 N or less was evaluated as good (◯), and a load exceeding the above range was evaluated as defective (×).
Sliding load (when sliding): Good when the difference ΔL between the sliding load L ₁ at start-up and the sliding load L ₂ at sliding is 45N or less (◯), and when the difference exceeds the above range is bad (×) As evaluated.

Presence / absence of stick-slip: The slide load waveform during sliding showed a smooth transition with no disturbance and was evaluated as no stick-slip (O), and the waveform with disturbance was evaluated as stick-slip (x).
The results are shown in Table 1.

表より、４０℃における動粘度が１５００ｍｍ²／ｓ未満である基油を用いた比較例１の潤滑剤組成物は、増ちょう剤としてＰＴＦＥを使用しているにもかかわらず、高荷重が加わった際に、スティックスリップが発生することがわかった。また、４０℃における動粘度が１３０００ｍｍ²／ｓを超える基油を用いた比較例２の潤滑剤組成物は、起動時のスライド荷重Ｌ₁が大きすぎることから、例えば、当該潤滑剤組成物を充てんした伸縮自在シャフトを中間軸としてコラム式ＥＰＳに組み込み、伸縮させて、ステアリングシャフトと舵取機構との間の距離を変化させながら、自動車に組み付ける際などには、その作業性が低下することが推測された。また、基油としては、４０℃における動粘度が１５００〜１３０００ｍｍ²／ｓの範囲内にあるものを使用しているものの、ＰＴＦＥ以外の増ちょう剤を使用した比較例３、４の潤滑剤組成物は、共に、高荷重が加わった際に、スティックスリップが発生することがわかった。

From the table, the lubricant composition of Comparative Example 1 using a base oil having a kinematic viscosity at 40 ° C. of less than 1500 mm ² / s is subjected to a high load despite using PTFE as a thickener. It was found that stick slip occurred when Further, the lubricant composition of Comparative Example 2 using a base oil having a kinematic viscosity at 40 ° C. exceeding 13000 mm ² / s has a too large slide load L ₁ at start-up. The workability of the filled telescopic shaft is reduced when it is assembled in a column-type EPS as an intermediate shaft, and is expanded and contracted to change the distance between the steering shaft and the steering mechanism while it is assembled in an automobile. Was guessed. In addition, as the base oil, the lubricant composition of Comparative Examples 3 and 4 using a thickener other than PTFE, although a kinematic viscosity at 40 ° C. is in the range of 1500 to 13000 mm ² / s. It was found that stick slip occurred in both objects when a high load was applied.

In contrast, the lubricant compositions of Examples 1 to 5 using a base oil having a kinematic viscosity at 40 ° C. in the range of 1500 to 13000 mm ² / s and using PTFE as a thickener are all used. Since the sliding load at the time of starting and sliding is within a favorable range, a telescopic shaft filled with these lubricant compositions is incorporated into the column-type EPS as an intermediate shaft, and is expanded and contracted. It was found that the workability can be improved when assembling to a car while changing the distance to the steering mechanism. Moreover, it was also confirmed that none of the lubricant compositions of Examples 1 to 5 produced stick slip even when a high load was applied.

It is a perspective view which shows the male spline part provided in the edge part of the inner shaft member which comprises the telescopic shaft of an example of embodiment of this invention. It is a perspective view which notches and shows a part of cylindrical female spline part provided in the edge part of the outer shaft member which comprises a telescopic shaft with the said outer shaft member. It is a schematic block diagram of column type EPS as an example of embodiment of the steering device of the present invention. It is a figure which shows the outline of the testing apparatus used in order to evaluate the characteristic of the lubricant composition prepared by each Example and the comparative example. It is a graph which shows an example of the relationship between the stroke amount of the axial direction of an inner shaft member, and a slide load measured using the test apparatus of FIG.

Explanation of symbols

1 Column type EPC (steering device)
2 Steering wheel (steering member)
3 Steering shaft 4, 6 Universal joint 5 Telescopic shaft (intermediate shaft)
51 Inner shaft member 51a Male spline portion 52 Outer shaft member 52a Female spline portion 7 Pinion shaft 8 Rack bar 11 Steering wheel A Rack and pinion mechanism

Claims (4)

A lubricant composition for lubricating between two shaft members of a telescopic shaft comprising a pair of shaft members that are extendable in the axial direction and coupled so as to be integrally rotatable in a rotation direction around the shaft. A lubricant composition comprising a base oil having a kinematic viscosity of 1500 to 13000 mm ² / s (40 ° C.) and polytetrafluoroethylene as a thickener.   The lubricant composition according to claim 1, wherein the content of polytetrafluoroethylene is 20 to 50% by weight.   A pair of shaft members that are extendable in the axial direction and coupled so as to be integrally rotatable in a rotation direction around the shaft are provided, and the space between both the shaft members is lubricated with the lubricant composition according to claim 1. Telescopic shaft characterized by that.   A steering member, a steering shaft connected to the steering member, an intermediate shaft connected to the steering shaft via a universal joint, and a pinion shaft connected to the intermediate shaft via a universal joint, and rotating the pinion shaft A steering apparatus having a rack and pinion mechanism for converting a linear motion of a rack bar to steer a steered wheel, wherein the telescopic shaft according to claim 3 is incorporated as an intermediate shaft. apparatus.

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